Mine firing mechanism



J. B. GLENNON ET AL 2,892,403

MINE FIRING MECHANISM 4 Sheds-Sheet 1 June 30, 1959 Filed sept. 18, 1941 INVENTORS J. B. GLENNON E. ROOT DI R. H.PARK E.S. GIL. LAN oRNEY June so, 1959 J. B. GLENNON ET AL 2,892,403

MINE FIRING MECHANISM 4 Sheets-Sheet 2 Filed Sept. 18, 1941 g5 48 51| 54 57 GIO 9 3 6 Im.. n 3. w` O T -a w m 2 E 4 R 2 l m.. B 5 2 9 6. 3 o RABCD wOT T rlvC MEM mmwmm-m ADQcmr..A

. S. G FIL LAN ATTORNEY June 30, `1959 J. B. GLENNON ETAL 2,892,403

- MINE lFIRING MECHANISM Filed Sept- 18. 1941 4 Sheets-Sheet', 5

lNvENToRs J. B. GLENHON E. ROOT III R. H.PARK

BY Mmmm June 30, 1959 J, B, GLENNON ET AL MINE FIRING MECHANISM Filed sept. 18, 1941 4 Sheets-Sheet 4 INVENTORS J. B. GLENNON E. R 0T D] R. H, PARK `countermining is rendered extremely remote.

the vacuum tube amplifier referred to hereinbefore.

United States Patent VMINE FIRING MECHANISM James B. Glennon, Washington, D C., Elihu Root ;III, New York, N.Y., Robert H. Park, Pluckemim NJ., and Edward S. Gilfllan, Manchester, Mass.

Application Septemher'l, 1941, Serial No. 411,318 32 Claims. (Cl. 102-1'8) L(Granted under ,'Ifitle 3.5, U.VS. Code (179,52), sec. 266) `'Ihisinvention relates to .aisubmarine mine in which the mine firing mechanism is rendered active in response to one of the characteristics of a vessel under way and in which the mine is fired by another of the characteristics of the vessel. More vspecifically the invention relates to a submarine mine of the moored type in which the presence of the vessel is first detected by waves or impulse of pressure within the water surrounding the mine and in which a vacuum tube amplifier is rendered effective Vto amplify signals received from an induction or gradiometer type of magnetic field sensing mechanism and in which an output signal from the amplifier is employed to operate a relay and detonate the mine.

In devices of the type heretofore proposed for controlling the operation of submarine mines, it has been the general practice to employ one `of the phenomena accompanying a moving vessel to sense the presence of the vessel and the same phenomenon to detonate the mine. Such devices have not proved entirely satisfactory in operation under all conditions of service for the reason that impulses or other signal conditions received from amine sweeper or as the result of countermining operations may `cause the mine to be prematurely detonated.

'The system of the present invention employs a plurality of different detecting devices and other instrumentalitiesin interconnected relation controlled by a timing mechanism for closing aplurality of electrical circuits in predetermined sequential order whereby the possibili-ty of premature detonation of the mine as the result of mine sweeping operations or as the result of In the illustrative embodiment Aof the `invention the mine is enclosed within a casing of sufficient size to impart to the mine a positive degree `of buoyancy such that the mine iioats at the end of a mooring cable substantially in a vertical position beneath the surface of the body of `water `within which Vthe mine is planted. Furthermore,

the mine is provided with an acoustic detecting device thereby to complete ,a cycle of `operations and activate The mine is also provided `with a pair of induction or gradiometer coils having their `axes Vin alinement with each Vother of detectingvthe gradient of the magnetic field set up by the vesseland al contact `mechanism closed at intervals during the operation of the timing device for applying the signals received by the coils through the vacuum tube .amplifier periodically at predetermined intervals of time. Upon receipt of a signal of predetermined magnitude from the gradiometer coils, the amplifiercauses a firing relaylto operate `and close a circuit to fire a detonator Itherebyexploding the mine.

One of the objects-of the invention is the provision of new .and improvedmeans ,forsensing the approach `0f @passing vessel; by one irlstrumntalityv `and causing 2,892,403 Patented June 3Q, 1959 ice the mine to be exploded in proximate relation toit-he vessel under control of a different instrumentality.

impro-ved means for firing a submarine mine inwhic'h `the .mme 1s armed in response to one of the natural phenomena accompanying a moving `vessel and firedunder control of a different one of the phenomena.

Another of the Vobjects is the provision vof means for causing a cycle of operations of a minefirng mechanism to be initiated by impulses of hydrostatic pressure and the mine to assume an armed Vcondition dur-ing the cycle of operations. i

Another of the objects resides in the provision of new and improved means for arming a submarine minefoi a predetermined period of time in response `to the operation rof an acoustic detecting device and for exploding the mine during the armed period thereof in `response to changes in the magnetic field detected by a field sensing device duringthe armed period of the mine.

Another of the objects resides in the provision of a mine ring mechanism in which .the firing of the mine is controlled by gradient signals receivedby a vvacuum 4tube amplifier at predetermined intervals .of time while the mine is in an armed condition.

Another objectresides in the provision of means settable at will for compensating for the differencein depth of immersion of the mine below the surface of the body of water within which the mine is moored.

Still other objects, advantages and improvementsfwill be apparent from the following description taken in connection with the `accompanying drawings, of Awhich:

Fig. 1 is a view, partly in section, of asubmarinemine according to a preferred embodiment of the-invention;

Fig. 2 is a view in section, taken substantially along the line 2 2 of Fig. 1;

Fig. 3 is a view, partly in section, `taken substantially along the line 3-3 of Fig. l;

Fig. 4 is -a view in diagrammatic form of a portion of the mine firing and control mechanism;

Fig. 5 isa timing diagram of the` circuit closing vdevice of Fig. 4; t r

,Fig-6 is a view in perspectivewof anacoustic device suitable for use with the system of the present invention;

Fig. 7 is a View in perspective, somewhatreduced, lof the device of Fig. 6 with the cover thereof in themas- `sembled position;

Fig. 8 is a View, somewhat enlarged, ,and partly in section taken `substantially along the line 8-8 .on-Fig. 6; and

Fig. 9 illustrates in diagrammatic form the circuit `arrangement of the entire system.

Referring now to the drawings on which like numerals of reference are employed throughout the several views to designate llike parts, and more particularlyrto Fig. Y1 thereof on which is shown a submarine mine comprising a casing l1 having a plurality of apertures 12` at one end thereof each adapted to receive an eye bolt or the like by means of which the mine is moored. Aixed tothe casing as by the bolts 14 is a cap 13, a suitable gasket 15 being inserted between the casing and vcap to seal the mine hermetically and prevent the seepage .of water therein. The casing 11 is also provided with a bulkhead or cap 16 secured thereto in any suitable manner in water-tight relation and having a recessed portionv OrA-well ,17 adapted to receive a hydrostat comprisinga member 18 in abutting relation with a shoulder 19 on, there cessed portion 17 .and maintained in;securerengagernent 121.6 percent iron.

therewith as by the threaded annular member 21, a ilexible diaphragm 22 being inserted between the annular member 21 and the member 18 to insure a water-tight "connection therebetween. The member 18 is adapted to receiveand support a plunger rod 23 having an enlarged end 24 thereon maintained inV engagement with the ilexvible diagram 22 as by the spring 25. Secured to the -plunger rod 23 in any suitable manner as by the nut 2 0 Vis a soluble washer 30 whereby movement of the hydrostat plunger is prevented until the mine has been submerged within the water for a predetermined period ottime. t Also secured to the plunger rod at the op- 1 posite end thereof is a detonator 26 having terminals adapted for external electrical connection as by the wires 27 disposed within a cable duct 28, the wires being of suiicient length to permit movement of the detonator within-'the booster `charge 29 as the hydrostat operates AinY response ltothe pressure of lwater within which the ,y mine is submerged.

An explosive charge 31 surrounds the well 17 within which the 'booster charge 29 is disposed, a bulkhead 32 being provided for retaining the explosive charge within the chamber thus formed. A cover 33 is provided for sealing the aperture 40 within the bulkhead 16 by ,means of which the explosive mixture 31 is introduced within the explosive chamber, the bolts 33' being provided to maintain 'the aperture in sealed condition after the explosive charge has been placed within the mine.

A channel shaped member 34 is disposed substantially throughout the length of the mine and provided with induction yor search coils 35 and 36 secured thereto as by the brackets 37 in such a manner that the axes of the coils are in alinement with each other. Each of the coils is provided with a magnetic rod or core 38 of material suitable for theV purpose such, for example, as soft iron or a material known in the trade as Permalloy having a composition of substantially 871/2 percent nickel and threaded and provided with adjustable discs 39 and 41 of magnetic material by means of which the etective Aflux linkages of the coils may be varied thereby to cause the signals generated by each of the coils in response to The ends of the core are preferably an identical changing condition in the magnetic eld within which the coils are disposed to be of the same order of magnitude. The coil 35is provided with an adjustable plate or disc 42 of magnetic material in threaded engagement with the core thereof having a plurality of adjustable rods or studs 43 of magnetic material extendl' ing radially therefrom and adapted to be set to different settings and locked by the nuts whereby the effective axis of the coil may be shifted or an angle of inclination may beimparted thereto whereby the axes of the coils may be brought into effective alinement with each4 other. The channel shaped member 34 is secured to a plurality of supports comprising a base 44 clamped to the annular bracing members 56 as by the bolts 45 and having a yieldable pad or cushion 46 secured thereto in any suitable manner as by. bonding the parts together, the

pad 46 also being bonded to the plate 47 to which the channel shaped member is attached by the bolts 60. A structure is thus provided in which the search coils and the channel shaped member are yieldably supported by 'the resilient member 46 thereby to prevent injury or damage to the search coils and the mine firing and control Vmechanism as the mine is launched.

of the mine thereby to strengthen and support the casing and prevent mechanical injury thereto during the handling, transportation and planting of the mine, each of the members 56 being provided with a suitable aperture 52 within which the search coils and mine coil mechanism are disposed.

A suitable arrangement of the control mechanism 49 is illustrated on Fig. 4, the mechanism comprising a mounting plate 57 to which is secured a battery S8 as by the clamps 59 and screws 61, the battery being provided with a plurality of terminals 62 for electrical connection to the vacuum tube amplifier and relaxation circuit control and timing mechanism. A second battery 63 preferably of somewhat lower voltage secured to the mounting plate 57 in themanner illustrated is also provided for lighting the filaments of the vacuum tubesemployed with the amplifier and selectively operating the detonator as willmore clearly appear as the description proceeds.

The mechanism of Fig. 4 also comprises a transformer 64 having electrical connections thereto including the conductors 65 in electrical circuit with the gradiometer coils 35 and 36, Fig. l, a condenser 66 being connected in parallel with the'gradiometer coils. The vacuum tube amplifier is indicated generally by the numeral 67, the amplifier including a power discharge type tube suchras the thyratron illustrated at 68 for operating the iiring relay 69 in response to a signal of sufficient magnitude received from the search coils. The control and selective closing of the various circuits of the mine firing mechanism is accomplished by the timing or cycling mechanism illustrated generally at 71 and operated by the successive operation of a relaxation circuit comprising a gaseous discharge tube 72 controlled jointly by signals received from the acoustic detecting device 53 over the conductor 73.

The cycling mechanism comprises an electromagnet `74 adapted to attract an armature 75 pivoted at 76 and provided with a pawl member 77 adapted to engage the teeth of the ratchet wheel 78 and advance the ratchet wheel through a predetermined angular distance during each operation of the armature 75. A ratchet 79 coacts with the pawl 77 to cause the ratchet wheel to be actuated during successive operations of the armature 75 and make a revolution or cycle of operations in response to signals received from the acoustic device. The ratchet wheel 78 is provided with a plurality of cams secured thereto and adapted to operate the contact springs 81, 82, and .83 in predetermined sequential orderduring a cycle of operations of the timing device thereby to control the mine iiringmechanism and circuits therefore according to a predetermined sequential order. A pair of contact springs indicated generally at 83 are adapted to be closed during each operation of the armature 75 thereby operatively to connect the gradiometer coils and condenser 66 by way of transformer 64 to the vacuum tube amplifier at intervals whereby the signals received from the gradiometer coils may be rendered elective to cause the amplier to deliver an output signal suicient to cause the operation of the tiring relay 69 and apply battery potential at 63 to the conductor 84 extending to the detonator 26 thereby to operate the detonator and tire the mine. Various other condensers and resistance elements and the circuit connections thereto are shown on Fig. 4, these elements being more particularly identified on Fig. 9 on which is shown in diagrammatic form the complete system. y

On Fig. 5 is shown a timing diagram of the operation 'of the control mechanism 71 during one cycle of operations or revolution thereof. For purposes of illustration the ratchet wheel 78 is assumed to be provided with 60 teeth and is therefore stepped ahead during 60 successive operations of the electromagnet -74 to complete a revolution or cycle of operations. The successiv@ Steps are indicated by the various numerals appearin g at the upper portion o f Fig. 5, beneath Awhich is shown a broken line indicating the operation of the acoustic detector. T he .contact A, it will `be noted, is caused to close once `during each operation .of the armature 75 or, in the timing device illustratedon Fig. 4, 60 timesduring a cycle of operations of the device. Contact B is normally in a closed position while the device 4is in a state of rest and is moved to open position during the third impulse received by the electromagnet 74, the `contact B resuming its closed state as the cam com- `pletes a revolution. Cam .contact Cis normally open and moved Vto closed position during the fourth operation of [the electromagnet 74, `the contacts remaining closed until thefty-eighth impulse has been received. .Cam contact .D is moved to closed position during the reception of the seventh impulse by the electromagnet and moved to open position as the fifth-seventh impulseis received.

vReferring now to Figs. 6, 7, and 8 there is shown .thereon the acoustic `detector 53 of Fig. l comprising a `mounting plate 8S adapted to receive and support a cover 86 `secured thereto as by the screws 87 having an `aperture 88 :therein within which are disposed the con- 4ductors 89. Also secured to the mounting plate is a support 91 vvhaving `the resilient device 92 clamped thereto as `by the plate 93 and mounting `screws 94 passing therethrough and in threaded engagement with the mounting plate185. A tube 95 preferably of brass or aluminum is .in rigid engagement with a base 96 and provided with an electrical contact 97. The base 96 is clamped by the lplate 98 and screws 99 to the resilient members 92 whereby the tube 95 and contact 97 are yieldably suplported by the resilient members 92 such that the contact 97 is adapted to vibrate in response to minute vibrationsthrough the mounting plate 85.

The contact 97 is normally in engagement with a contact 100 at one end of a pivoted bar 110 mounted on a .shaft 101 pivoted as at 102 and 103 respectively. A ,sensitive spring 104 secured at one end thereof to the shaft 101 and at the other end thereof to the arm 105 .extending from the member 106 threaded on the adjusting screw `107' `whereby the degree of pressure between the contacts 97 and 100 when no vibrations are received may be varied at will in accordance with the setting of ,the adjusting screw.

The screw member 107 passes through an aperture within the support 108 and is maintained in the adjusted positionby the spring washer 109. The adjusting screw 107 is provided with a ltapped hole .in axial alinement .with the screw within which is disposed the pivot bear- ,ing 111.

A support 112 having a tapped hole within which is disposed the threaded member 113 having a pivot screw 114 therein is mounted upon the base 85 and secured thereto by the screw 115. A lock nut 116 is provided for maintaining the screw member 113 in the adjusted position with respect to the support 112. A bar 117 is secured to the supports 108 and 112 as by the screws 118 and provided with a recessed portion within which is disposed a resilient member 119 for iarresting the pivotedbar 110 when `vigorously actuated by .the vibrating tube 95. The supports 108 and 112 and the pivoted bar 110fare electrically insulated from the base 85 by means of the strip of insulating material 122 and the insulating washers 123 and bushings 124 inserted therebetween. The support 112 is provided with a screw `125 in threaded engagement therewith whereby one of 'the conductors 89 is in electrical circuit with the contact 100 and in electrical disengagement with the base 85 when the Contact is disengaged from the contact 97. The other of the the conductors 189 is in circuit with the base 85 and the contact 97 by reason of the terminal `thereof being cllampedbeneath the head of one of the it be assumed, by `way-of example. Ithat aczluble washer has been placed inoperative position .withinqthe mine and that the timing device TD has the cam elements thereof at rest in their normal or `home positions and, `furthermore, that the mine has been launched within a .bodyof water of vsutlicient depth to Acause the extender hydrostat to operate when the soluble washer has dissolved or softened sufficiently to permit movement of the hydrostat in response to the pressure of the water. The ,hydrostat switch element 126 is normally maintained'in engagement with contact `127 and disengaged from Vcontact 128 thereby maintaining a ground potential on conductor 129 and positivelypreventing the operation of the relax- .ation circuit and timing device until the hydrostat is moved to the operated or armed position. With `the hydrostat unoperated, ground is removed from one end of the detonator 26 thereby positively pre-venting the operation of the detonator and premature tiring of the mine during the handling, transportation, and planting of the same. When `the `mine has been planted for a period of time suicient to cause the hydrostat to operate, the contact element 126 thereof is disengaged from contact 127 and moved into engagement with contact y128. The mine is now in a partially armed condition.

Let it be assumed that a vessel moves` into the threshold of sensitivity of the acoustic device such that the vibrations from the ships propulsion vsystem are received through the water by the acoustic .detector 53 thereby causing the detector to operate suiciently to disengage contact 97 from contact 100 thereof. When this occurs, ground at conductor 131 is removed from `one end of the resistance element 132 thereby causing the relaxation circuit comprising the gaseous discharge tube 133 to operate in the following manner.

Condenser 134, it will be noted,-is charged at this time substantially to the potential of the battery BA, the condenser charging circuit including a high resistance 135, and the plate of the tube 133 has a potential applied thereto substantially equal to the potential of the battery. The resistance 135 is connected to resistance 136 by the conductor 130, resistance 136 being connected to resistance 132, the point of connection between the resistances also being connected to condenser and the grid of the tube. The resistance units 136 and 132 are thus arranged to comprise a potentiometer having one end thereof connected to the positive terminal of the battery BA by way of resistance 135 and the other end connected by way of conductor 137, contacts of cam B, conductor 138, contacts 100 and 97 in engagement with each other, conductor 13,1 and thence to ground whereby the potential of the grid of the tube 133 is maintained below the ring potential of they/tube, the condenser 140 being charged to this potential. As the contacts of the acoustic detector are disengaged, ground is removed from conductor 137 extending to one end of the resistance 132 thereby causing a rising potential to be applied to the grid of the tube and the charge on condenser 140 to be increased. The resistance 136 is relatively high whereby the charging current for the condenser 140 is maintained at a relatively-low value and the increase in voltage at the grid of the tube is thus accomplished at a slow rate whereby the grid potential is not increased sufficiently to fire the tube as the acoustic detector contacts are disengaged momentarily for the first time in response to the vibrations received from the vessel.

As the contacts 100 and 97 are engaged momentarily the charge on condenser 140 is reduced by the flow of current through the resistance 132. It will be noted, however, that the detector contacts are open during-relatively greater intervals of time than the time during which the contacts are closed whereby more current flows into the condenser 140 than ows out of the condenser. The charge on condenser 140 is thus gradually increased and the potential of the grid of'the tube133 is lalso A tube to re.

increased during successive operations of the detector contacts until suicient potential is attained to cause the When this occurs a circuit is completed from positive potential on conductor 130, through tube 133, conductor 139, winding of stepping magnet STP and thence lto ground thereby causing the magnet STP to operate and the condensers 134 and 140 to be discharged until the voltage on the plate of the tube is reduced suiiiciently to extinguish the tube thereby interrupting the discharge circuit through condensers 134 and 140 and causing the stepping magnet to release.

As the stepping magnet operates in response to the tiring of the tube 133, armature 141 thereof moves away from the back stop 145 and into the operated position engage the next succeeding tooth of the ratchet wheel 143. The operation of the stepping magnet also causes contact A to engage spring 163 and close a circuit from ground at conductor 164, gradient coils GC, conductor 165, contact A, conductor 166, primary winding P of the transformer T and thence to ground, the circuit including a condenser 167 in parallel connection with the gradient coils. The condenser 167 is charged to a potentian proportional to the gradient of the magnetic iield detected by the coils GC. This potential is applied suddenly to the transformer T by the closure of the contacts 163, but the gradient signal detected at this time is ineiective for the reason that the filaments of the tubes of the amplifier are not in a heated condition.

As the voltage across the condenser 134 falls below the potential required to maintain a discharge within the tube 133, the tube is extinguished and the stepping magnet STP releases and causes the spring contacts 163 to be disengaged thereby interrupting the circuit between the condenser 167 and the primary winding of the transformer T. The release of the stepping magnet causes the armature 141 to be moved by the retractile spring 144 into the released position in engagement with the back stop 145 thereby advancing the cam assembly to position 1. A ratchet spring 146 prevents movement of the ratchet wheel in the reverse direction as the pawl 142 is withdrawn to the next succeeding tooth thereof.

The charge on condenser 134 is now increased by current flowing through resistance 135 and the charge on condenser 140, with the detector contacts in open position, is increased by curren-t flowing through resistance 136 until sufficient potential is applied to the plate and grid of the tube to cause the tube ito tire. When this occurs the stepping magnet STP is again operated thereby connecting the gradiometer coils GC and condenser 167 to winding P of lthe transformer by way of contact spring 163 and contact A and the pawl 142 is moved into engagement with the next succeeding tooth of the ratchet wheel 143. The relatively low impedanceV of the discharge circuit causes the gaseous discharge tube 133 to lbe extinguished thereby interrupting the circuit to the stepping magnet and causing armature 141 thereof to be released and the cam assembly of the timing device to be advanced to position 2.

As the cam assembly is moved into position 3 in response to a third impulse received from the relaxation circuit, the cam B contacts are open thereby disconnecting the acoustic detector contacts from the resistance 132 and insuring that the relaxation circuit will continue 'to operate cyclically and cause the cam assembly of the timing device to be stepped ahead until cam B closes at the completion of the instant revolution of the cams or until the mine is exploded, as the case may be.

As the cam assembly moves into position 4 in response to a fourth impulse received from the relaxation circuit, the contacts of cam C are closed thereby applying battery by way of cam C contacts, conductor 147, resistance 148, conductor 149, filament of tube 151, and thence by way of conductor 152 to ground, the circuit also including the laments of tubes 153 and 154 in series, connected in parallel with the lament of tube 151. The tubes 153 and 154 may be of any type suitable for the purpose such, for example, as Raytheon tubes known in the trade as CKSOS-AX and the tube 151 may be of any type in which the plate discharge current is maintained continually in response to a tiring potential applied to the grid of the tube such, for example, as a thyratron tube known in the trade as RK62. The closure of cam C contacts also applies battery by way of conductor 147 to armature 168 of the firing relay FR.

As the cam assembly of the timing device moves into position 7 cam D contacts are closed thereby short circuiting resistance 154 and applying battery at 155 by way of conductor 156, cam D contacts, conductor 157, winding'o-f relay FR and resistance'lSS in'paralle1',conduc'tor c S 159 and thence to the plate of the thyratron tube 151. The mine is now in an armed condition.

Each operation of armature 141 of the timing device causes springs 163 to close contact A and connect the gradiometer coils GC and condenser 167 to the winding P of the transformer T. The vessel, it will be recalled, is continually approaching the mine during this time whereby the gradient signals stored within the condenser 167 and applied periodically to the transformer are'of an ever increasing order of magnitude. These signals are applied to the grid of the tube 154 by the winding S of the transformer and amplilied by the vacuum tube arnplier during the approach of the vessel until a signal is transmitted by the tube 151 of sufficient strength to cause the tiring relay FR to operate. The vessel, it will be understood, has moved ahead during this time to a position such that it is substantially directly above the mine, the distance through which the vessel has moved being determined by the setting of the variable resistor element 161 in circuit with the grid of the vacuum tube 153. An arrangement is thus provided whereby the degree of amplification or gain Within the amplier may be varied at will in accordance with the setting of the variable resistor element 161 and the mine may be caused to explodeV under a predetermined portion of the vessel in accordance with the setting of the variable resistor.

The operation of relay FR at armature 168 thereof closes a circuit from battery by way of cam C contacts, conductor 147, armature 168 and make contact of relay FR, conductor 169, detonator 26, conductor 171, contact 128, contact element 126 and thence to ground thereby causing the detonator to operate and explode the mine.

In the event that the signals received by the amplifier during the movement of the cam assembly of the timing device TD from position 7 to position 57 thereof are not sufficient in strength to cause the operation of the tiring relay FR, the mine is -not exploded and the operation of the timing device continues until the cams thereof are moved into the normal or home position at the completion of the sixtieth impulse received by the stepping magnet STP.

As cam D moves into position 57 the cam contacts D are disengaged thereby removing the short circuit from resistance 154 which is of suiiiciently high order of magnitude to prevent the operation of relay FR as the filament circuit to the amplifier is interrupted at cam C contacts during the movement of cam C into position 58. As the cam assembly moves into position 60 cam B contacts are closed thereby applying ground at conductor 131, by way of contacts 97 and 100 of the acoustic detector, conductor 138, cam B contacts, conductor 137 and resistance 132 to the grid of the tube 133 thereby decreasing the voltage of the grid to a value below the tiring potential and effectively preventing additional iring of the tube and further operation of the timing device at this time. l

The resistance 158 is provided in parallel with the winding of the relay FR to insure that the voltage drop across the relay as the tube 151 fires is insufcient to cause the plate voltage of the tube to be decreased to such a value that the arc between the lament and the ,plategof .the tubeis extinguished. The tiring -.voltage. applied to zthe Tgrid .ofthe tube 151 isofrelatively `short duration Vand the .,continuanceof .the arc within the tube depends upon the .maintenance.ofasustainedvoltage of predetermined .minimum `value on the plate ofthe tube. Theuse ofthe vresistance 158 in .the manner disclosed .providesalow impedancepathin .the plate rcircuit of the tubein parallel with the windingof relay FR whereby the .plate voltage Vis maintained 4at a predetermined `value .afterthe fringpotentil has-been removed from the grid `anda current is thus ,continuously maintained through the relay -windingof suliicientstrength to preventthere- ,lease-ofthe relay after the tube has been fired.

Briefly ,stated .in summary, the kpresent `invention contemplates .theiprovision .of a mine firing mechanism in whichthe mine is caused tofassume an armed condition inresponse to waves or impulses of hydrostatic pressure received from the propeller of an approaching vessel and `in whichvthe firing of `thefminelis controlled by the Ygrad- .fient of'the'tmagneticrtield detected ,by'fa` field sensing mechauismand in whichthe explosion of'lthe mine is delayed until theivessel isidirectly above the lmine. Furthermore, '.the system ofthe present invention `comprises means settabl'eat :will for compensatingfor thedepth of the body of vwater lwithin which the mine fmay .be .planted and .'for Ainsuring `that the :mine will .explode .only in response vto `the-passage 'ofza'vessel .of atleast a'predetermined size.

While :the rinvention has been 4described with particular'ity 'as .to one `'preferred `embodimentof a `combination :of-mechanismsi'and Voffeach `of rthe elements ofthe com- Ibination, .it lis to ibe'understoodxthat this 'has been done for purposes ofdisclosure/and thatvarious changes and :substitutions Vmay be readily apparent vto those skilled in the artto whichthe invention pertains, after understanding `the invention hereindisclosed, 'and that the terms employed in the appended claims are to be considered as words of descriptionrather than vWords of limitation.

The invention herein disclosed and claimed may 'be manufactured `and used by or for the Government ofthe .United States of America 'for governmental purposes without the -payment of any royalties-thereon or therefor.

4What is claimedas new and desired to be secured by Letters Patent of the United States is:

l. In a submarine mine of the v'character disclosed,

lrneans including an acoustic detecting device 'for sensing the approach o fa vessel, a timing `device adapted to be controlledby said acoustic detecting device, a vacuum tube amplifier in electrical connectionwith said timing deviceymeans for detectingthe gradient of the magnetic fieldof'saidvesseL 'meanscontrolle'd by saidtiming device Lkfor operatively connecting said 'gradient detecting 'means atintervalstothe amplifier during `a cycle of oper- 'atiousof the4 timing device, detonating means, 'andmeans contrlledby sfdampliiierfor causing M'the mine-to be "explodedby 'said Adetonatirig l*means when Ythe gradient si'gnal'receivedby 4,said Vdetecting-means has reached a predetermined value.

2. In'a submarine mine of the `character disclosed, "means responsive rto a disturbance of Yacoustic character 'cause'dby `a vessel'in motion for detecting the `approach "fthevesse'l, means for sensing `a disturbance'of magnetic t':'haracter caused ybymovernent ofthe Ivessel, a normally "de-energized i'sig'nl :amplifier adapted lto amplify :signals "receive'dfrom said "sensing means, 'means controlled by said detecting means for causing the amplifier-to be=enV fergized'for a predetermined'period oftime, a detonating -device, and means 'operatively.connectedto ysaid ampli- "ferffor causingl'the 'detonating device toexplode. theV mine whenithe signalszreceived'from thepisensingimeans during fsaid Tpredetermined period vof :time thave :reached la pretdetermined strength.

3. AIn a'submarinefmine` of the character disclosed disposed Vwithin a f magnetic field; means responsive to=vibraftions 1atv-i'thinl the 'water Areceived Vfrom f a vessel in: motion viferdetectingiftl'lenapproacliof -thetvesseh meansforrsens- .ing a .change .within..said.magnetic :field caused .by the .movement voi `the vessel .Within the vicinity kof themine,

a,plurality.of.circuits, means adaptedto .be controlled ,by vsaiddetecting `means forclosing said plurality of circuits .in ,predetermined sequential order, a normally de-ener- `.gized signal :amplifyingdeviceadapted to be connected by one ofsaidcircuitsto saidsensing.meansinaccordance `with the operated condition of one of said `circuit .closing,means, means including another of saidrcircuit vof `a vessel, meansincluding Yapair of normallyengaged .contacts for detecting vibrations, received from the vessel, `a normally.inactive'relaxation circuitcomprisinga gaseous discharge.tubecontrolled .by said normally closed `contacts, a .timing mechanism, an electro-responsive vdevice ,in-circuit Awith the `discharge path of `said tube for .actuatingsaid'mechanisrn through apredetermined cycle of operations in `response to the disengagement of said `contacts as vibrations are received by said detecting means, circuit closing means .included in said timing mechanism andtoperable during said predetermined cycle of operations, means for sensing the gradient of Athe magnetic field caused by the movement of said vessel within the vicinityof the mine,vmeans controlledby said .timing mechanisnrfor generating signals vat regularintervals of vtime inzaccordance with the gradient of `the magnetic eld sensed ,by said sensing means, a vacuum tube amplifier controlled by -said circuit closing means and ,adapted to receive and amplify said signals during said predeterminedcycle-ofoperations, andi means including an electro-,responsive device operatively connectedto said amplifier -for causingthe mine to be exploded when the amplified signals `are of a predetermined strength.

5. `In a` submarine mine of the character disclosed disposed Within amagnetic field adjacent the path of travel of a vessel, an acoustic detector having a pair `of closed `contactsadapted to be disengaged as the detectoroperates, va `timing device having a rotatable member actuatable to ahome position and to a plurality of moved positions duringv a cycle of operations of the device, contact means, `means for maintaining said contact means in closeden- ,gagement when the rotatable member is in the home position and `for causing the `contact means to be disengaged .duringthe actuationof the rotatable member through said .moved positions, vmeans including a Vgaseous discharge l.tube .rforrcausing the timing ldevice to make said cycle of `operations .inresponse tothe operation of said acoustic 4detector ,..means :for detecting a change `in said magnetic `field caused by the movement of said vessel withinthe Vvicinityof :the `mine, and .means effective during said cycle of Aoperations of the timing device for causing the .mine' to beexploded'in response to a signal of predetermined strengthreccived from said detecting means.

6. In a .submarine mine of the character disclosed dispoSed within'amagnetic eld adjacent the path of travel :rangedrwithinza` magnetic field` adjacent the path of travel tof'tavesselnanfacoustic11deviee'fordetecting the approach ofthe vessel, a timing mechanism controlled by said acoustic device, a pair of gradiometer coils adapted to detect a change in said magnetic field caused by the approach of the vessel, a condenser connected in parallel vwith said gradiometer coils, signal amplifying means,

means included within said timing mechanism for operativelyconnecting said gradiometer coils and condenser to the amplifying means at intervals during the operation of said timing mechanism, an electro-responsive device operatively connected to said signal amplifying means and selectively operable in accordance with the strength of signals received from said signal amplifying means, and means including a detonating device for causing the mine to be exploded in response to the operation of said electroresponsive-device.

8. A mine firing mechanism of the character disclosed comprising a timing mechanism operable in unit cycles, means for causing said timing mechanism to make a predetermined number of unit cycles of operation, means vincluding an acoustic device responsive to vibrations recycles, means for causing said timing mechanism to make a predetermined number of cycles of operation,v means including an acoustic device responsive to vibrations received from an approaching vessel for initiating the operation of said timing mechanism, means effective when the timing mechanism has made less than said predetermined number of cycles of operation for rendering the Yacoustic device ineffective, a normally inactive vacuum tube amplifier, means controlled by said timing mechanism for activating said amplier during said predetermined number of unit cycles of operation of the timing mechanism, means for sensing the gradient of the magnetic field of an approaching vessel, means for operatively connecting said sensing means to the amplifier at intervals during said cycles of operation of the timing mechanism, electroresponsive means selectively operable in accordance with the strength of the signals received from the amplifier, and means including a detonating device controlled by said electroresponsive means for causing the mine to explode when the signals received from the amplifier have reached a predetermined strength.

v10. ,In a submarine mine of the character disclosed disposed within a magnetic field adjacent the path of travel of a vessel, an electrical circuit, a timing device having means for closing said electrical circuit, means including" an acoustic detector responsive to vibrations received from an approaching vessel for causing said timing'device to make a cycle of operations, means including a pair of gradiometer coils for generating signals in accordance with the gradient of the magnetic field caused ,bythef approaching vessel during said cycle of operations of the timing device, a firing relay adapted to be operated selectively in accordance with the strength of signals received by said signal Vgenerating means, a detonating devicea firingcircuit for said ydetonating device controlled by said firing relay, and means including said electrical circuit for closing in part said firing circuit during a cycle of operations of said timing device. p v v 11. In a submarine mine of the character disclosed arranged within a magnetic field adjacent the path of travel of a vessel, an acoustic device adapted to respond to vibrations for detecting the approach of the vessel, a relaxation circuit comprising a normallyY inactiveI grid glow discharge tube controlled'by said acoustic device, timing mechanism operatively connected to said relaxation s 12 Y circuit and adapted to make a predetermined number of cycles of operations, said mechanism comprising a plurality of contact elements operable in predetermined order during said cycles of operations of the mechanism, a normally inactive signal amplifying device, means controlled by at least one of said contact elements for rendering the signal amplifying device active during a predetermined number of cycles of operations of the timing mechanism, sensing means for detecting the gradient of the magnetic field caused by the approaching vessel, means controlled by said timing mechanism for applying signals to the signal 'amplifying device at intervals in accordance with the gradient of the magnetic field detected by said sensing means, detonating-means, and electro-responsive means controlled by the signals received fromrsaid signal amplifying device for operating the detonating means during :a predetermined` number of cycles of operations 'of said timing mechanism. Y

l2. In a submarine minetof the character disclosed arranged within a magnetic field adjacent the path of travel of a vessel, an acoustic device adapted to respond to vibrations received from the vessel for detecting the approach of the vessel, a relaxation circuit comprising "a normally inactive grid glow discharge tube controlled by said acoustic device, timing mechanism operatively connected to said relaxation circuit and adapted to make a predetermined number of cycles of operations, said mechanism comprising a plurality of contact elements operable in predetermined order during said cycles of operations of the mechanism, a normally inactive signal amplifying device, means controlled by at least one of said contact elements for rendering the signal amplifying device active during a predetermined number of cycles of operations of the timing mechanism, means for sensing the gradient of the magnetic field caused by the approaching vessel, means controlled by said timing mechanism for applying signals at intervals to the signal amplifying device in accordance with the gradient of the magnetic field detected by said sensing device, detonating means, electro-responsive means controlled by the signals received from said signal amplifying device for operating the detonating means during a predetermined number of cycles of operation of said timing mechanism, and means settable at will for varying the degree of amplification of saidsignal amplifying device. v Y' 13. In a submarine mine of the character disclosed disposed withina magneticiield adjacent the path of travel of a vessel, arpaair'of serially connected coils .adapted to generate signals of varying degrees of strength in accordance with the gradient o f the magnetic field caused by a vessel moving within the vicinity of the mine, va condenser connected in parallel with said coils and adapted to store said signals, a normally inactive vacuum. tube amplifieiga transformer device operatively -'connected to ythe input of said amplifier for. receiving the `stored signals, an acoustic device adapted to respond to vibrations received from said vessel, timing mechanism controlled by said acoustic ,device for causing the amplier-to be activatedl for a predetermined period of time, means controlled by the timing mechanism for repeatedly applying the stored signals to said transformer device during said predetermined period of time, and means controlled by said amplifier for causing the mine to explode when the signals applied torsaid transformer have reached a predetermined degree of strength. Y f

14. In a submarine mine of the character disclosed moored within a magnetic field adjacent the path of travel '.13 of stime, Vmeans for ;:m'omentarily applying the stored-sig nals in succession-tto said .amplifier .during .said period ;.of time, 1a firing zrelayin .electrical circuit with Atheplate Vof tube.

15. #In asubmarine mineof the character disclosed arranged -within a magnetic field, means including an .acoustic detecting device responsive yto vibrations received Ifrom .a moving -vesselgfor .arming the'mine, vmeans for detectingthe gradient of :the .magnetic `field caused by the .moving vessel, said detecting means ,comprisinga .pair of .searchcoils having .two bars `of magnetic materialrespec- .tively disposed inaxial alinement with'each other,'and

meanseffective when the Vmineis in an armed condition .,forcausing themine-to ,be-exploded selectively .in accordance withf the degreeofethe `gradient of said .magnetic iield tdetcctedbyasaid detecting means.

16. In a submarine mine of the character disclosed a1'- l ranged .within a magnetic field adjacent the path of travel Aof a yessel, means `includingan acoustic device responsive to vibrations .received -frorn .an approaching vessel for arming the mine, meansincluding a pair-of search coils .connected'in series opposition and disposed in spacerelation with respect-t0 each other .for generating signals in accordance .with the gradient of .the magnetic field detected bythe coils, means settable at will for bringing the axis of one of .said coils into .alinement with `the axis of the other Vof" the coils, and means controllediby the signals received from said pair of search coils vfor causing the armed mine .tobe `exploded under said vessel. s

17. In a moored submarinemine .of the character disclosed arranged within a magneticiield adjacent the path yof travelof `a vessel, `means controlled by the -.pressure of `the body o'ftwater -within which the mine is moored for partiallylarming the mine, 4means .responsive to vibrations V'received from an approaching vessel for additionally arming the mine, detonating means, and means responsive to "the gradientiofthe-magnetic .field of -said vessel for causing ithe m'inetofbe exploded. bysaiddetonating means when 'the mine .has been additionally armed.

18. `Inra :moored submarine mine ofnthe character disclosed arranged within a magnetic eld adjacent the path of travel of a vessel, means including timing means responsive to vibrations received from a vessel approaching within the vicinity of the mine for arming the mine for a predetermined period of time, means adapted to detect the gradient of a changing magnetic field caused by the approach of said vessel during said predetermined period of time, and means for disarming the mine when the gradient of said magnetic field is not detected during said predetermined interval of time.

19. In a moored submarine mine arranged within a magnetic field adjacent the path of travel of a vessel, means including an acoustic device responsive to vibrations received from an approaching vessel for arming the mine, a pair of search coils connected in series opposition adapted to generate signals in accordance with the differential in the flux linkages of the coils with said magnetic field, a pair of magnetic bars disposed in axial alinement with each other within the coils respectively for increasing the flux linkages of the coils with said magnetic field, magnetic means arranged on at least one of said bars and settable at will for causing the flux linkages of the coils to be equal in number when the eld within which the coils are disposed is uniform in character, and means including a detonating device for causing the mine to explode selectively in accordance with the strength of the signal corresponding to the gradient .of the xmagnetic I,fieldtof said 1approaching -yessel .detected by said search coils when the mine has been armed.

.20. .In a .submarine .amine `o f the `character .disclosed `adapted to .be moored Twitlgrin Ka :body of `water adjacent .the path of .travel `.o f a moving Nessel, ,.a-.casingfor said mine, .an lacoustic: ldevice secured to said casing and re- ,sponsi-veto tvibrationsswithinrthe watersreceivedlfrom said Wessel, timing mechanism v.controlled .by .said .acoustic device, .a `pair ,of .opposedly .connected search .coils .for

.generating signals finV accordance .with .the gradientY of .the

.magnetic Lfield `of :said .moving .vessel .detected `by the coils, means forsupporting said. search coils and timing mechanism .in g predetermined .space relation .with `respect to each other, meansffor iyieldablymounting said sup- ;porting nneans :within .said casing, `means controlled .by

the timing mechanism for amplifying said signals, and ,means including .a detonating device .controlled by the 'Signal amplifrinstmeaps @fer sensing themine te explode -selectivelyin accordance'swith thestreng'thf .theamplimeans responsive toasdisturbance of `.acoustic .character caused by a yesselin motion for A,detecting ,the .approach vof the vessel, .means jfor..sensing .a .disturbance of magnetic ,character caused bytrnovement .of the vessel within .the damage zone-.of zthe mine, means ...controlled by Ysaid deteetng means fer arming the minefandmeans responsiveto the sensingmeans .forcausing the .armed mine te esplode 22. In a device of the character disclosed, .a mine, .means responsive to vibrations for detecting theapproach of -a vessel, means controlled by said .detectingmeans for arming the mine,.andmeans-responsive to armagnetic condition controlledv by .the proximity of .the ,vessel for causing the `armed mine `to explode.

23. In Va device ofthe character disclosed arranged within-a magneticfield .adjacent .thepath of travel of a vessel, .a mine, means responsive-to vibrations received from an approaching vessel, means `controlled by .said vibration responsive means for arming the mine, and `means controlled by the gradient of the magnetic field of the vessel for causing .the armed mine to explode.

24. AIn a v,submarine .mine ofthe `character disclosed, means vresponsiveto vibrations for detecting the approach of a vessel, means responsive `tos-proximity of said vessel, apparatus ,operatively connected tosaid proximity rresponsive means and :normally unresponsive thereto, means controlled by said detecting y'nneanswwhen .a vessel is :approaching for rendering said apparatus responsive to said proximity responsive means for a predetermined period of time, a detonating device, and means operatively connected to said apparatus for causing the detonating device to explode the mine when the proximity responsive means responds to a vessel during said predetermined period of time.

25. In a device of the character disclosed, a mine, means including timing means responsive to vibrations received from a vessel approaching Within the vicinity of the mine for arming the mine for a predetermined period of time, and means responsive to a magnetic condition controlled by the proximity of the vessel to the mine for causing the mine to explode when the magnetic condition increases to a predetermined value during said predetermined interval of time.

26. In a device of the character disclosed, a mine, means for generating low frequency signals variably in accordance with changes in a magnetic condition associated with a vessel moving with respect to the mine, means including timing means responsive to vibrations Vreceived from the vessel and adapted to convert said low :apredetermined 'value during'said predetermined interval yof, time. v

` 27. In a 'device of the character disclosed, la mine,

'means for generating low frequency signals variably in accordance with changes in a magnetic condition associated with a vessel moving with respect to the mine,

"ing the mine to explode when the magnetic condition reaches a predetermined vale'during said predetermined interval of time.

' 28. In a device of the character disclosed, a mine,

means including a pair of contacts adapted to be opened and closedV in responseI to vibrations received from a vessel moving within the vicinity1 of the mine, electrical tilningcontrolV means adapted-to arm the mine for a predetermined' interval of"time,"*means controlled by said vibration responsive means "forinitiating operation of said 'control means when a' predetermined relation exists between theopenv and closed times of lsaid pair of contacts,

and'means responsive to a magnetic condition controlled by the proximity of the vessel 'to the mine for causing the mine to explode vwhenthe magnetic condition increases to a predetermined value during said predetermined ini 29. Ina submarine mine ofthe character disclosed arranged within a magnetic'iield'adjacent the path of travel of a vessel, a mine tiring system including acoustic means for said tiring circuit Vadapted to permit the mine vfiring ,f'circuit action if the magnetic gradient signals, receivedby the-magnetic gradient detecting means are of ,ai predetermined duration, and a detonating means in said system adapted to be armed by said arming circuit andfiired -by said circuit.

30. A mine ring mechanism of the character disclosed comprising an electrical mine arming circuit, an electrical mine tiring circuit, signal detectingV means operatively connected to said arming circuit and adapted to arm the mine upon reception of an acoustic signal from a passing vessel, a magnetic field detecting means in said firing circuit, a normally inactive amplifier in said arming'circuit adapted when activated to be responsive to signals received by the magnetic detecting means, a detonating means in said firing circuit adapted to be armed by said arming circuit, and a timing means adapted to be set in operation by action of said signal detecting meansand adapted to control the arming and firing of the mine. I'

31. In a device of the character disclosed arranged for use in Vaisnbmarine mineadapted to be Vmooredwithin-a Y magnetic field adjacent the pathfof travel of a vessel, 'a hydrostatic switch for partially arming the mine, means responsive to vibrations received from an approaching vessel for additionally arming the mine, means including timing means responsive to said received vibrations for controlling the armed period ofthe mine, and means responsive to a magnetic conditionc'ont'rolled by the proximity of the vessel for causing the armed mine to explode.

32. In a moored submarine mine of the character disclosed arranged within a magnetic field adjacent the path of travel of a vessel, a hydrostatic switch for partially arming the mine, means responsive to vibrations received vfrom an approaching vessel for' additionally arming the mine, means controlled by said vibration responsive means and including timing means for timing the armed period of the mine, and means controlled by the gradient of the magnetic field of the moving vessel for causing the armed mine to explode.

Vacquier Sept. 3, 

